Recently, technologies have arisen that allow near field coupling (such as wireless power transfers (WPT) and near field communications (NFC)) between electronic devices in close proximity to each other and more particularly, thin portable electronic devices. Both near field coupling functions use radio frequency (RF) antennas in each of the devices to transmit and receive electromagnetic signals. Because of user desires (and/or for esthetic reasons) many of these portable devices are small, are becoming smaller as markets evolve, and have exaggerated aspect ratios when viewed from the side (i.e., they are “thin”). As a result, many of these thin devices incorporate flat antennas which use coils of conductive material as their radiating (or radiation receiving) antennas for use in near field coupling functions.
However, the small form factor of many devices interferes with the ability of the coils to couple. For instance, objects within the devices and near the coils might divert the flux of the magnetic field away from the coils. Notably, metallic objects tend to divert magnetic flux around themselves and, thus, away from the coils. Moreover, it might be the case that users want to transfer power and/or communicate using the devices without generating a strong magnetic field. Instead, users might prefer to use the often-limited onboard power of these devices to affect other functions (for instance, placing phone calls, receiving phone calls, accessing data over RF wide area networks such as the Internet, etc.).
In addition, users tend to prefer to hold certain devices and/or to set them down in certain orientations. For instance, some devices provide NFC functions by “bumping” the backs of two devices together. This back-to-back bumping is intended to place the coils in the two devices in close proximity to each other and in such a relative orientation that the coils couple relatively well. In some cases the location, shape, etc. of the two coils correspond to each other relatively closely during back-to-back bumps. Yet, for ergonomic reasons, users holding these devices might find it awkward to hold them in an orientation suitable for back-to-back bumping. In other instances, users might wish to affect WPT between the devices while using (or having available for use) one or both devices. Thus, to perform WPT from a laptop computer to a cellular telephone (for instance) users often do not wish to lay the cellular telephone on top of the keyboard of the laptop device (where the relative orientation and proximity of the coils facilitates their coupling). In many cases, users instead prefer to orient the devices involved in a side-by-side configuration. In other words, users often want to bump one side of one device to a side of another device in NFC scenarios and want to leave one device next to another in lengthier WPT scenarios, which often require some time to occur.
Unfortunately, with many small form factor (and, more specifically, “thin”) devices, side-by-side device orientations limit the ability of the coils in the devices to couple. In such relative orientations, the coils might be rather distant from one another and/or one coil might sense only the field generated at the edge of the other coil. Thus, placing such devices side-by-side might limit the rate at which WPT occurs because the portion of the field which the receiving coil happens to be in is so weak (or the relative orientation of the flux is such) as to limit the coupling of the receiving antenna with the magnetic field. In NFC scenarios, the bit rate associated with the communication can be similarly limited by the weak coupling of the coils. Similar considerations also apply to the transmitting coil and its ability to propagate the field in the presence of tightly integrated objects within the transmitting device. Yet users desire WPT and NFC functionality in an increasing number (and variety) of thin devices and they desire those functions with side-by-side operability.
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